Electron Configurations and Periodic Properties

5.3

Atomic Radii

• Atomic radius – ½ the distance between the nuclei of identical atoms that are bonded together. • Can be difficult to measure

Atomic Radius

• Trend: • Decreases across a period–b/c effective nuclear charge

• Increases down a group–more E levels / electron shielding

Atomic Radii

Ionization Energy

• You can remove an e- from an atom if enough E is supplied• A + energy = A+ + e-• The A+ is an ion of that atom w/ +1

charge

Ionization Energy• Ion – atom or group of bonded atoms

that has a + or – charge• Ionization – any process that results in

the formation of an ion• Ionization energy – the E required to

remove 1 e- from a neutral atom of an element (aka First Ionization Energy IE1

Ionization Energy

Ionization Energy

• The Trend–Increase across a period•B/c increase effective nuclear charge

–Decrease going down the group•e- further out – electron shielding

Removing e- from + ions

• If enough E is supplied, you can remove more e-• Called second ionization E, or third

ionization E, & so on• 2nd and 3rd are always higher than

previous b/c effective nuclear charge

Electron Affinity

• Electron Affinity – the E change that occurs when an e- is acquired by a neutral atom• Some give off E = A + e- A- + E• Some require E = A + e- + E = A-

–These are unstable and hard to determine

Electron Affinity

• Trend:• Increases across a pd (except nob. gas)–Increasing nuclear charge

• Decreases down a group–Increase in e- shielding b/c larger atomic

radius

Electron Affinity

• 2nd e- affinities are always more positive (requires more E) than 1st e- affinities

Ionic Radii

• Cation – a positive ion–Made from the loss of an e-–Creates smaller radii

• Anion – a negative ion–Addition of 1 or more e-–Creates a larger radii

Ionic Radii

• Trend …• Cationic and anionic radii decrease

across a pd –B/c increasing nuclear charge

• Both increase down a group

Ionic Radii

Valence Electrons

• V.E. – e- available to be lost, gained, or shared in the formation of chemical compounds• Located in incompletely filled main-E

levels• For MGE – located in outermost s&p

Electronegativity

• e-neg – a measure of the ability of an atom in a chemical compound to attract e- from another atom in the cmpd.• Trend… (NOBLE GASES EXEMPT)• Increase across pd. • Decrease down a group

Electronegativity

Properties of the d and f block

• Not as straight forward as the others• e- fill in lower E levels for these

blocks so some differences occur• Some E levels promote or demote e-

to obtain more stability (4s13d5)